Ornamental · Poaceae
Annual Ryegrass
Lolium multiflorum
Sow it in fall and annual ryegrass throws up fine glossy blades, hungry roots, and a stand that mostly bows out by spring.
Full sun
Every 3–7 days
50–120 days
USDA 6–9
Overview
Annual ryegrass is the cover crop for dressing bare ground in a hurry. It is a cool-season bunchgrass of the genus Lolium, and its narrow leaves emerge a deep, polished green that catches the light along every blade. It germinates and roots faster than almost anything else you can sow, and growers use it to hold soil over winter, take up leftover nitrogen, and feed grazing animals.
It is no relation to cereal rye and stands apart from its perennial cousin up close. This is a true annual that runs its whole life in one season, lifting slender flower spikes in spring and browning back as heat or cold arrives. That short life is useful, since a stand that dies on its own spares a termination pass.
The trait to watch sits in those spikes. Annual ryegrass packs each one with seed and can be stubborn to kill, so a stand left to ripen scatters fresh blades through fields and margins as a weedy volunteer. Cut at the right moment it serves the soil; left to head it turns into a problem.
Care
The short version: the fine glossy blades come up best from seed sown shallow into moist soil in full sun and kept watered while they establish, and they hold most soils on their own. Mowing stays no closer than 3 to 4 inches, and the stand is terminated at early bloom before it seeds.
Light
Annual ryegrass colors up deepest in full sun but takes partial shade in stride. More light packs the slender blades closer and pushes the stand up faster, which is what a cover crop wants as it knits over bare ground.
Water
The fine blades stay lush on steady soil moisture and curl and dull in drought. Sustained heat and dry weather scorch them outright, though the plant carries its green through wet and even briefly flooded soil better than most cover crops.
Soil
Few grasses root this readily across so much ground. The blades fill in over clay, loam, sand, rocky, and high-organic soils across a wide pH of 5.0 to 7.5, growing thickest and glossiest in rich, moist, well-drained loam.
Temperature
This is a cold-tolerant grass whose blades hold from about 10°F to 81°F (-12°C to 27°C). They stay vivid in cool weather and fade once summer heat sets in, which is why the seed goes down for fall and spring.
Humidity
Outdoor humidity leaves no mark on the foliage, so there is no figure to meet. What sets the color and vigor of the blades is moisture in the soil, the source of their quick germination and early growth.
Feeding
The blades green up on no feeding at all most of the time, drawing leftover soil nitrogen up through the roots rather than living off fertilizer. A nitrogen source at planting suits only genuinely poor soils.
Pruning
Mowing holds the blades as living mulch or temporary turf, but never closer than 3 to 4 inches, since the crowns need leaf left to regrow. To end the stand, terminate at early bloom by mowing, tilling, or a contact herbicide, since shearing the tops alone may not finish off an established crown.
Repotting
none
Size & spacing
Grown as a stand of slim blades rather than spaced plants, it rises 1 to 3 feet (30 to 91 cm) tall, with each plant tufting only about 8 to 12 inches (20 to 30 cm) wide. The seeding rate, not spacing, sets how tightly the blades pack.
When to plant
Annual ryegrass is a cool-season grass, its blades growing in the cooler shoulders of the year rather than the heat of summer. Direct sow it from late summer into fall to carry green leaves through winter in mild zones, or in early spring, and in cold country get the seed down at least 40 days before the first killing frost. The slim flower spikes rise in spring, the cue to terminate before seed sets.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: not typically started indoors; direct sown
- Plant: Late summer to early fall (late July through October) for overwintering in mild zones, or early spring; in zone 5 and colder sow at least 40 days before first killing frost
- Harvest: Flower spikes in spring; terminate before seed set. As a cover crop, biomass is produced over fall, winter and spring.
Hardiness
USDA hardiness zones: 6–9
Temperature: down to -23°C
Troubleshooting
Trouble with annual ryegrass shows in the look of the blades and spikes, and it comes down to timing and control more than disease. The main risks are letting the spikes set seed, browning and gapping from winter or drought, and a thin, scattered start from dry ground. Match what the stand shows below and act before a small problem spreads into the next crop.
Fresh seedlings spear up as volunteers
Once the spikes mature, each one cradles its seed and lets it scatter, and the next season is studded with new green blades. A single plant releases about 300 seeds of very high viability, and a mower simply shears the tops while the crowns live on, more so where populations resist glyphosate. Cutting the stand at early bloom by disking, plowing, or a contact herbicide ends it before those slim seedheads ever ripen.
Fix:
- Terminate at early bloom before seed set by disking, plowing, or a non-persistent contact herbicide
- Use a chaff/seed collection system at harvest if grown to seed nearby
- Repeat control passes since seeds germinate in both fall and spring across a wide temperature range (36 to 104 degrees F)
Glossy green gives way to brown winter patches
When the bright blades brown and collapse in ragged patches, that is winterkill, worst in zone 5 and colder where no snow blankets the crowns. Summer heat and drought above about 80°F (27°C) scorch the leaves to the same straw color and thin the stand. Sowing at least 40 days before the first killing frost gives the roots time to grip down, while in self-clearing systems the browning blades are exactly the end that was wanted.
Fix:
- Reseed bare areas in mild zones, or accept winterkill where a self-terminating cover is desired
- Plant early enough (at least 40 days before first killing frost) so plants establish before cold
Sparse, thin blades after sowing
When only scattered blades pierce the surface, dry soil is nearly always behind it, since the seed leans on steady moisture to throw up its first thin shoot, and seed buried too deep exhausts itself before reaching daylight. Tucking it at 1/4 to 1/2 inch deep and watering when rain falls short brings an even flush. A sound rate of about 10 to 20 lb per acre drilled or 20 to 30 lb broadcast fills the thin spots with fine green leaves.
Fix:
- Sow at 1/4 to 1/2 inch depth and ensure rainfall or irrigation for good establishment
- Use proper seeding rates (10-20 lb/acre drilled, 20-30 lb/acre broadcast)
Toxicity
As a lawn or cover crop, the slim glossy blades of annual ryegrass are safe around cats and dogs, which at most get a mild upset stomach from chewing grass. The real warning rides in the seedheads: ryegrass infected with fungal endophytes carries alkaloids that cause ryegrass staggers in horses and grazing livestock, a tremor and incoordination syndrome. Graze or cut it before those spikes form.
Toxic to
Horses · Rabbits · Livestock · Birds · People
Safe for
Cats · Dogs
Horses Moderate
Grazing endophyte-infected ryegrass can throw a horse into ryegrass staggers, with muscle tremors, a stiff or spastic gait, and stumbling that sharpens the instant the horse is stressed or asked to move. The ergot bodies that swell dark in the seedheads carry alkaloids that also pinch the blood vessels tight.
Rabbits Caution
The young, clean blades are ordinary forage, but the same fungal alkaloids that affect grazing livestock can gather in mature growth thick with seedheads. Rabbits do best on the fine green leaves and away from heading or endophyte-affected stands.
Livestock Moderate
Cattle, sheep, and goats grazing affected pasture can take on the same staggers from lolitrem B, trembling and dropping when they grow excited or try to run. The ergovaline beside it draws the blood vessels narrow and dulls their condition.
Birds Caution
The slim ryegrass seed turns up across many bird diets and is no recognized poison. The catch is the ergot swollen in mature seedheads, so birds should not load up on heavy, fungus-marked grain.
People Caution
No part of these blades is meant for the plate, so there is nothing to gather and eat. The real nuisance for people is the fine pollen the spring spikes throw off, a well-known driver of hay fever in late spring.
Cats None
The slim green blades carry no toxin, and the ASPCA lists no hazard for them. A cat that bites off a glossy blade or two may bring a little back up, and that is the whole of it.
Dogs None
The soft, glossy foliage is safe for dogs as a lawn or cover crop. A mouthful of the leaves brings nothing worse than the mild, passing stomach upset any grass can.
Safe as a lawn, forage, or cover-crop grass around pets; the foliage itself is non-toxic to cats and dogs. For pastured horses and livestock, manage endophyte- and ergot-affected seedheads - cut or graze before heading and avoid feeding affected, mature ryegrass.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
A few distinct types share the ryegrass name, and up close the blades and spikes set them apart. These are the ones worth telling apart before you buy seed.
Annual / Italian ryegrass (Lolium multiflorum)
This is the fast cover-crop and forage type, a short-lived cool-season bunchgrass whose bright, glossy leaves catch the light, and it usually winterkills in cold zones.
Perennial ryegrass (Lolium perenne)
A close relative grown for turf and pasture that pushes up fresh blades year after year, unlike the annual Lolium multiflorum that dies off each season.
Westerwolds annual ryegrass
A true-annual form of Lolium multiflorum that throws up its flower spikes and sets seed in its very first season without a cold spell, prized for fast, single-season cover or forage.
Diploid vs tetraploid types
Tetraploid cultivars carry doubled chromosomes that swell their leaves and seeds larger and juicier with better palatability, while diploids crowd into denser, finer-bladed stands.
How to propagate
Annual ryegrass grows one way, from slim seed sown straight into the ground, and the first fine blades come up fast.
SeedEasy
Late summer to early fall for overwintering, or early spring; sow at least 40 days before first killing frost in cold zones · Germinates and establishes very quickly, often within 1-2 weeks in moist cool soil
The slim ryegrass seed goes straight into the ground and never starts indoors. Late summer to early fall sowing carries the green blades through winter, early spring is the other window, and in cold zones the seed wants to be down at least 40 days before the first killing frost. Broadcast at 20 to 30 lb per acre or drill at 10 to 20 lb per acre, just 1/4 to 1/2 inch deep, into moist soil, and the first fine shoots break the surface within a week or two.
Myths
Annual ryegrass is the same plant as cereal rye.
The two share a word in their names and look nothing alike up close. Annual ryegrass is Lolium multiflorum, a fine-bladed forage and turf bunchgrass, while cereal rye is Secale cereale, the tall, very cold-hardy grain that goes into bread. Two different grasses from two different genera, so the seed and the growing advice for one will not carry over to the other.